I guess the Health and Safety boys of today would not like it even though the Octal plug was used for many such applications in the past. Just make sure you fit the socket on the power supply and arrange for the amplifier not to have any charged capacitors lurking on the detached plug. I try to use connectors that have a certain amount of shrouding on both halves, even recessed pins are better than fully exposed ones, especially if exposed pins can be touched whilst actually making contact with the socket.

I also make sure the psu "knows" the HT connector is terminated before energising the HT. In my case, continuity between the sheild of the BNC and the chassis. This then operates a relay to switch the ht on after a short delay to let the cathodes warm.